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Sep 19, 2013
09/13

by
MIrna Dzamonja; Istvan Juhasz

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We give a construction under $CH$ of a non-metrizable compact Hausdorff space $K$ such that any uncountable semi-biorthogonal sequence in $C(K)$ must be of a very specific kind. The space $K$ has many nice properties, such as being hereditarily separable, hereditarily Lindel\"of and a 2-to-1 continuous preimage of a metric space, and all Radon measures on $K$ are separable. However $K$ is not a Rosenthal compactum. We introduce the notion of bidiscrete systems in compact spaces and note...

Source: http://arxiv.org/abs/0910.3091v2

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Sep 21, 2013
09/13

by
Michal Hajdusek; Vlatko Vedral

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We present a closest separable state to cluster states. We start by considering linear cluster chains and extend our method to cluster states that can be used as a universal resource in quantum computation. We reproduce known results for pure cluster states and show how our method can be used in quantifying entanglement in noisy cluster states. Operational meaning is given to our method that clearly demonstrates how these closest separable states can be constructed from two-qubit clusters in...

Source: http://arxiv.org/abs/0902.4343v2

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Sep 19, 2013
09/13

by
Pramod Kumar Mishra

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Lattice model of directed self avoiding walk has been solved analytically to investigate adsorption desorption phase transition behaviour of a semiflexible sequential copolymer chain on a two dimensional impenetrable surface perpendicular to the preferred direction of the walk of the copolymer chain in three dimensions. The stiffness of the chain has been accounted by introducing an energy barrier for each bend in the walk of the copolymer chain. Exact value of adsorption desorption transition...

Source: http://arxiv.org/abs/0909.4653v3

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Sep 22, 2013
09/13

by
Eli Visbal; Abraham Loeb; Stuart Wyithe

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21cm emission from residual neutral hydrogen after the epoch of reionization can be used to trace the cosmological power spectrum of density fluctuations. Using a Fisher matrix formulation, we provide a detailed forecast of the constraints on cosmological parameters that are achievable with this probe. We consider two designs: a scaled-up version of the MWA observatory as well as a Fast Fourier Transform Telescope. We find that 21cm observations dedicated to post-reionization redshifts may...

Source: http://arxiv.org/abs/0812.0419v3

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Sep 22, 2013
09/13

by
Saad Zaheer; Sahand Jamal Rahi; Thorsten Emig; Robert L. Jaffe

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We investigate the electromagnetic Casimir interactions of an object contained within an otherwise empty, perfectly conducting spherical shell. For a small object we present analytical calculations of the force, which is directed away from the center of the cavity, and the torque, which tends to align the object opposite to the preferred alignment outside the cavity. For a perfectly conducting sphere as the interior object, we compute the corrections to the proximity force approximation (PFA)...

Source: http://arxiv.org/abs/0908.3270v2

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Sep 22, 2013
09/13

by
R. V. Mishmash; I. Danshita; Charles W. Clark; L. D. Carr

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We present a fully quantum many-body treatment of dark solitons formed by ultracold bosonic atoms in one-dimensional optical lattices. Using time-evolving block decimation to simulate the single-band Bose-Hubbard Hamiltonian, we consider the quantum dynamics of density and phase engineered dark solitons as well as the quantum evolution of mean-field dark solitons injected into the quantum model. The former approach directly models how one may create quantum entangled dark solitons in...

Source: http://arxiv.org/abs/0906.4949v4

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Sep 19, 2013
09/13

by
Alessandro Soncini; Liviu F. Chibotaru

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We investigate the spin transport through strongly anisotropic noncollinear magnetic molecules and find that the noncollinear magnetization acts as a spin-switching device for the current. Moreover, spin currents are shown to offer a viable route to selectively prepare the molecular device in one of two degenerate noncollinear magnetic states. Spin-currents can be also used to create a non-zero density of toroidal magnetization in a recently characterized Dy_3 noncollinear magnet.

Source: http://arxiv.org/abs/0910.5235v3

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Sep 21, 2013
09/13

by
Dibyendu Roy

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We study two simple mesoscopic models of interacting two electrons; first one consists of two quantum coherent parallel conductors with long-range Coulomb interaction in some localized region and the other is of an interacting quantum dot (QD) side-coupled to a noninteracting quantum wire. We evaluate exact two-particle scattering matrix as well as two-particle current which are relevant in a two-particle scattering experiment in these models. Finally we show that the on-site repulsive...

Source: http://arxiv.org/abs/0905.3881v2

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Sep 19, 2013
09/13

by
Nicolas Ressayre

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Let $G$ be a complex semisimple simply connected algebraic group. Given two irreducible representations $V_1$ and $V_2$ of $G$, we are interested in some components of $V_1\otimes V_2$. Consider two geometric realizations of $V_1$ and $V_2$ using the Borel-Weil-Bott theorem. Namely, for $i=1, 2$, let $\Li_i$ be a $G$-linearized line bundle on $G/B$ such that ${\rm H}^{q_i}(G/B,\Li_i)$ is isomorphic to $V_i$. Assume that the cup product $$ {\rm H}^{q_1}(G/B,\Li_1)\otimes {\rm...

Source: http://arxiv.org/abs/0910.0697v2

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Sep 21, 2013
09/13

by
S. Gupta; R. Kumar; R. P. Malik

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We demonstrate a few striking similarities and some glaring differences between (i) the free four (3 + 1)-dimensional (4D) Abelian 2-form gauge theory, and (ii) the anomalous two (1 + 1)-dimensional (2D) Abelian 1-form gauge theory, within the framework of Becchi-Rouet-Stora-Tyutin (BRST) formalism. We demonstrate that the Lagrangian densities of the above two theories transform in a similar fashion under a set of symmetry transformations even though they are endowed with a drastically...

Source: http://arxiv.org/abs/0905.0934v3

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Sep 21, 2013
09/13

by
Stephen C. Anco; Amanullah Dar

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For the Euler equations governing compressible isentropic fluid flow with a barotropic equation of state (where pressure is a function only of the density), local conservation laws in $n>1$ spatial dimensions are fully classified in two primary cases of physical and analytical interest: (1) kinematic conserved densities that depend only on the fluid density and velocity, in addition to the time and space coordinates; (2) vorticity conserved densities that have an essential dependence on the...

Source: http://arxiv.org/abs/0902.3405v3

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Sep 23, 2013
09/13

by
Dachun Yang; Dongyong Yang; Yuan Zhou

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Let ${\mathcal X}$ be a space of homogeneous type in the sense of Coifman and Weiss and ${\mathcal D}$ a collection of balls in $\cx$. The authors introduce the localized atomic Hardy space $H^{p, q}_{\mathcal D}({\mathcal X})$ with $p\in (0,1]$ and $q\in[1,\infty]\cap(p,\infty]$, the localized Morrey-Campanato space ${\mathcal E}^{\alpha, p}_{\mathcal D}({\mathcal X})$ and the localized Morrey-Campanato-BLO space $\widetilde{\mathcal E}^{\alpha, p}_{\mathcal D}({\mathcal X})$ with...

Source: http://arxiv.org/abs/0903.4576v2

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Sep 19, 2013
09/13

by
Patrick Erik Bradley

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A $p$-adic variation of the Ran(dom) Sa(mple) C(onsensus) method for solving the relative pose problem in stereo vision is developped. From two 2-adically encoded images a random sample of five pairs of corresponding points is taken, and the equations for the essential matrix are solved by lifting solutions modulo 2 to the 2-adic integers. A recently devised $p$-adic hierarchical classification algorithm imitating the known LBG quantisation method classifies the solutions for all the samples...

Source: http://arxiv.org/abs/0910.4839v2

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Sep 21, 2013
09/13

by
Hanfeng Li; Anthony Weston

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Doust and Weston introduced a new method called "enhanced negative type" for calculating a non trivial lower bound p(T) on the supremal strict p-negative type of any given finite metric tree (T,d). In the context of finite metric trees any such lower bound p(T) > 1 is deemed to be non trivial. In this paper we refine the technique of enhanced negative type and show how it may be applied more generally to any finite metric space (X,d) that is known to have strict p-negative type for...

Source: http://arxiv.org/abs/0901.0695v3

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Sep 19, 2013
09/13

by
A. Marshakov; A. Mironov; A. Morozov

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The AGT relations allow one to convert the Zamolodchikov asymptotic formula for the conformal block into the instanton expansion of the Seiberg-Witten prepotential for theory with two colors and four fundamental flavors. This provides an explicit formula for the instanton corrections in this model, resolving in this way an old problem in Seiberg-Witten theory. The answer is especially elegant for vanishing matter masses, then the bare charge of gauge theory 16q_0 = 16e^{i\pi\tau_0} plays the...

Source: http://arxiv.org/abs/0909.3338v3

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Sep 23, 2013
09/13

by
B. Ivlev

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Quantum tunneling through a two-dimensional static barrier becomes unusual when a momentum of an electron has a tangent component with respect to a border of the prebarrier region. If the barrier is not homogeneous in the direction perpendicular to tunneling a fraction of the electron state is waves propagating away from the barrier. When the tangent momentum is zero a mutual interference of the waves results in an exponentially small outgoing flux. The finite tangent momentum destroys the...

Source: http://arxiv.org/abs/0903.5100v3

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Sep 19, 2013
09/13

by
Ricardo A. Mosna; Gustavo Marques Tavares

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We present a systematic study of spherically symmetric self-dual solutions of SU(2) Yang-Mills theory on Euclidean Schwarzschild space. All the previously known solutions are recovered and a new one-parameter family of instantons is obtained. The newly found solutions have continuous actions and interpolate between the classic Charap and Duff instantons. We examine the physical properties of this family and show that it consists of dyons of unit (magnetic and electric) charge.

Source: http://arxiv.org/abs/0909.5145v2

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Sep 22, 2013
09/13

by
Brian A. Munson; Ismar Volic

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We study the spaces of string links and homotopy string links in an arbitrary manifold using multivariable manifold calculus of functors. We construct multi-cosimplicial models for both spaces and deduce certain convergence properties of the associated Bousfield-Kan homotopy and cohomology spectral sequences when the ambient manifold is a Euclidean space of dimension four or more.

Source: http://arxiv.org/abs/0906.2589v3

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Sep 22, 2013
09/13

by
H. -M. Guo; M. Franz

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Electrons hopping on the sites of a three-dimensional pyrochlore lattice are shown to form topologically non-trivial insulating phases when the spin-orbit (SO) coupling and lattice distortions are present. Of 16 possible topological classes 9 are realized for various parameters in this model. Specifically, at half-filling undistorted pyrochlore lattice with SO term yields a 'pristine' strong topological insulator with Z2 index (1;000). At quarter filling various strong and weak topological...

Source: http://arxiv.org/abs/0908.0698v2

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Sep 22, 2013
09/13

by
Daniel Rudoy; Prabahan Basu; Patrick J. Wolfe

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In this article we introduce a broad family of adaptive, linear time-frequency representations termed superposition frames, and show that they admit desirable fast overlap-add reconstruction properties akin to standard short-time Fourier techniques. This approach stands in contrast to many adaptive time-frequency representations in the extant literature, which, while more flexible than standard fixed-resolution approaches, typically fail to provide efficient reconstruction and often lack the...

Source: http://arxiv.org/abs/0906.5202v2

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Sep 21, 2013
09/13

by
Y. Zhou; J. H. Jiang; M. W. Wu

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We investigate electron spin relaxation in $p$-type GaAs quantum wells from a fully microscopic kinetic spin Bloch equation approach, with all the relevant scatterings, such as the electron-impurity, electron-phonon, electron-electron Coulomb, electron-hole Coulomb and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings explicitly included. From this approach, we examine the relative importance of the D'yakonov-Perel' and Bir-Aronov-Pikus mechanisms in wide ranges of...

Source: http://arxiv.org/abs/0905.2790v2

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Sep 23, 2013
09/13

by
Su-Chan Park

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Although Hinrichsen in his unpublished work theoretically rebutted the possibility of the discontinuous transition in one-dimensional nonequilibrium systems unless there are additional conservation laws, long-range interactions, macroscopic currents, or special boundary conditions, we have recently observed the resurrection of the claim that the triplet creation model (TC) introduced by Dickman and Tom\'e [Phys. Rev. E {\bf 44}, 4833 (1991)] would show the discontinuous transition. By extensive...

Source: http://arxiv.org/abs/0903.3436v3

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Sep 19, 2013
09/13

by
Federico I. Pelupessy; Padelis P. Papadopoulos

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We use time-varying models of the coupled evolution of the HI, H_2 gas phases and stars in galaxy-sized numerical simulations to: a) test for the emergence of the Kennicutt-Schmidt (K-S) and the H_2-pressure relation, b) explore a realistic H_2-regulated star formation recipe which brings forth a neglected and potentially significant SF-regulating factor, and c) go beyond typical galactic environments (for which these galactic empirical relations are deduced) to explore the early evolution of...

Source: http://arxiv.org/abs/0910.4905v2

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Sep 22, 2013
09/13

by
Hadi Salmasian

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We show that irreducible unitary representations of nilpotent super Lie groups can be obtained by induction from a distinguished class of sub super Lie groups. These sub super Lie groups are natural analogues of polarizing subgroups that appear in classical Kirillov theory. We obtain a concrete geometric parametrization of irreducible unitary representations by nonnegative definite coadjoint orbits. As an application, we prove an analytic generalization of the Stone-von Neumann theorem for...

Source: http://arxiv.org/abs/0906.2515v2

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Sep 19, 2013
09/13

by
G. Tommei; A. Milani; D. Vokrouhlicky

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The radioscience experiment is one of the on board experiment of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian (PN) parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This...

Source: http://arxiv.org/abs/0910.5818v2

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Sep 23, 2013
09/13

by
Shi Pu; Sang-Jin Sin; Yang Zhou

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We build a holographic description of non-relativistic system for superconductivity in strongly interacting condensed matter via gauge/gravity duality. We focus on the phase transition and give an example to show that a simple gravitational theory can provide a non-relativistic holographical dual description of a superconductor. There is also a critical temperature like the relativistic case, below which a charged condensation field appears by a second order phase transition and the (DC)...

Source: http://arxiv.org/abs/0903.4185v3

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Sep 20, 2013
09/13

by
Oscar J. C. Dias; Jose' P. S. Lemos

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We study in detail the quantum process in which a pair of black holes is created in a higher D-dimensional de Sitter (dS) background. The energy to materialize and accelerate the pair comes from the positive cosmological constant. The instantons that describe the process are obtained from the Tangherlini black hole solutions. Our pair creation rates reduce to the pair creation rate for Reissner-Nordstrom-dS solutions when D=4. Pair creation of black holes in the dS background becomes less...

Source: http://arxiv.org/abs/hep-th/0410279v3

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Sep 19, 2013
09/13

by
Raghunandan H. Keshavan; Sewoong Oh

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We consider the problem of reconstructing a low-rank matrix from a small subset of its entries. In this paper, we describe the implementation of an efficient algorithm called OptSpace, based on singular value decomposition followed by local manifold optimization, for solving the low-rank matrix completion problem. It has been shown that if the number of revealed entries is large enough, the output of singular value decomposition gives a good estimate for the original matrix, so that local...

Source: http://arxiv.org/abs/0910.5260v2

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Sep 20, 2013
09/13

by
D. Cohen; G. Denham; M. Falk; A. Varchenko

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If F is a master function corresponding to a hyperplane arrangement A and a collection of weights y, we investigate the relationship between the critical set of F, the variety defined by the vanishing of the one-form w = d log F, and the resonance of y. For arrangements satisfying certain conditions, we show that if y is resonant in dimension p, then the critical set of F has codimension at most p. These include all free arrangements and all rank 3 arrangements.

Source: http://arxiv.org/abs/0907.0896v2

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Sep 23, 2013
09/13

by
S. Mazoyer; F. Ebert; G. Maret; P. Keim

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We investigate the dynamics of a glass forming 2D colloidal mixture and show the existence of collective motions of the particles. We introduce a mean square displacement MSD with respect to the nearest neighbors which shows remarkable deviations from the usual MSD quantifying the individual motion of our particles. Combined with the analysis of the self part of the Van Hove function this indicates a coupled motion of particles with their cage as well as intra cage hopping processes.

Source: http://arxiv.org/abs/0903.4675v4

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Sep 19, 2013
09/13

by
Christoph Lehner; Tilo Wettig

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We calculate the partition function of partially quenched chiral perturbation theory in the epsilon regime at next-to-leading order using the supersymmetry method in the formulation without a singlet particle. We include a nonzero imaginary chemical potential and show that the finite-volume corrections to the low-energy constants $\Sigma$ and $F$ for the partially quenched partition function, and hence for spectral correlation functions of the Dirac operator, are the same as for the unquenched...

Source: http://arxiv.org/abs/0909.1489v2

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Sep 19, 2013
09/13

by
A. Crisanti; C. De Dominicis; T. Sarlat

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The spin glass behavior near zero temperature is a complicated matter. To get an easier access to the spin glass order parameter $Q(x)$ and, at the same time, keep track of $Q_{ab}$, its matrix aspect, and hence of the Hessian controlling stability, we investigate an expansion of the replicated free energy functional around its ``spherical'' approximation. This expansion is obtained by introducing a constraint-field and a (double) Legendre Transform expressed in terms of spin correlators and...

Source: http://arxiv.org/abs/0909.2556v2

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Sep 19, 2013
09/13

by
Heesang Park

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We construct a minimal complex surface of general type with $p_g=0$, $K^2 =4$, and $\pi_1=\mathbb{Z}/2\mathbb{Z}$ using a rational blow-down surgery and a $\mathbb{Q}$-Gorenstein smoothing theory. In a similar fashion, we also construct a symplectic 4-manifold with $b_2^+=1$, $K^2=5$, and $\pi_1=\mathbb{Z}/2\mathbb{Z}$.

Source: http://arxiv.org/abs/0910.3476v2

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Sep 19, 2013
09/13

by
Raghunandan H. Keshavan; Andrea Montanari; Sewoong Oh

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We consider a problem of significant practical importance, namely, the reconstruction of a low-rank data matrix from a small subset of its entries. This problem appears in many areas such as collaborative filtering, computer vision and wireless sensor networks. In this paper, we focus on the matrix completion problem in the case when the observed samples are corrupted by noise. We compare the performance of three state-of-the-art matrix completion algorithms (OptSpace, ADMiRA and FPCA) on a...

Source: http://arxiv.org/abs/0910.0921v2

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Sep 19, 2013
09/13

by
Amelia M. Stutz; George H. Rieke; John H. Bieging; Zoltan Balog; Fabian Heitsch; Miju Kang; William L. Peters; Yancy L. Shirley; Michael W. Werner

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We present Spitzer observations of a sample of 12 starless cores selected to have prominent 24 micron shadows. The Spitzer images show 8 and 24 micron shadows and in some cases 70 micron shadows; these spatially resolved absorption features trace the densest regions of the cores. We have carried out a 12CO (2-1) and 13CO (2-1) mapping survey of these cores with the Heinrich Hertz Telescope (HHT). We use the shadow features to derive optical depth maps. We derive molecular masses for the cores...

Source: http://arxiv.org/abs/0910.5476v2

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Sep 19, 2013
09/13

by
Giuseppe Carleo; Marco Tarzia; Francesco Zamponi

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The role of geometrical frustration in strongly interacting bosonic systems is studied with a combined numerical and analytical approach. We demonstrate the existence of a novel quantum phase featuring both Bose-Einstein condensation and spin-glass behaviour. The differences between such a phase and the otherwise insulating "Bose glasses" are elucidated.

Source: http://arxiv.org/abs/0909.2328v2

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Sep 18, 2013
09/13

by
Nick Gill; Anupam Singh

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We classify the real and strongly real conjugacy classes in $GL_n(q)$, $SL_n(q)$, $PGL_n(q)$, $PSL_n(q)$, and all quasi-simple covers of $PSL_n(q)$. In each case we give a formula for the number of real, and the number of strongly real, conjugacy classes.

Source: http://arxiv.org/abs/0809.4412v2

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Sep 19, 2013
09/13

by
D. Eckert; V. Savchenko; N. Produit; C. Ferrigno

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Aims. We use the IBIS/ISGRI telescope on-board INTEGRAL to measure the position of the centroid of the 20-200 keV emission from the Crab region. Methods. We find that the astrometry of the IBIS telescope is affected by the temperature of the IBIS mask during the observation. After correcting for this effect, we show that the systematic errors in the astrometry of the telescope are of the order of 0.5 arcsec. In the case of the Crab nebula and several other bright sources, the very large number...

Source: http://arxiv.org/abs/0910.1698v2

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Sep 22, 2013
09/13

by
Sourin Das; Sumathi Rao; Arijit Saha

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We study transport through a single channel t-stub geometry strongly coupled to a superconducting reservoir. In contrast to the standard stub geometry which has both transmission resonances and anti-resonances in the coherent limit, we find that due to the proximity effect, this geometry shows neither a T=1 resonance (T is the transmission probability for electrons incident on the t-stub) nor a T=0 anti-resonance as we vary the energy of the incident electron. Instead, we find that there is...

Source: http://arxiv.org/abs/0811.0660v4

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Sep 21, 2013
09/13

by
Chunlei Liu; Wenxin Liu; Chuanze Niu

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The $T$-adic exponential sum associated to a Laurent polynomial in one variable is studied. An explicit arithmetic polygon is proved to be the generic Newton polygon of the $C$-function of the T-adic exponential sum. It gives the generic Newton polygon of $L$-functions of $p$-power order exponential sums.

Source: http://arxiv.org/abs/0901.0354v6

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Jul 20, 2013
07/13

by
Taras Banakh; Tatsuhiko Yagasaki

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We prove that the group D^r(R) of C^r diffeomorphisms of the real line, endowed with the compact-open and Whitney C^r topologies, is bihomeomorphic to the group H(R) of homeomorphisms of the real line endowed with the compact-open and Whitney topologies. This implies that the diffeomorphism group D^r(R) endowed with the Whitney C^r topology is homeomorphic to the countable box-power of the separable Hilbert space.

Source: http://arxiv.org/abs/0804.3645v3

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Sep 22, 2013
09/13

by
S. W. Zhang; L. Ma; Y. D. Hou; J. S. Zhang; T. L. Xia; G. F. Chen; J. P. Hu; G. M. Luke; W. Yu

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We performed $^{75}$As NMR studies on two overdoped high-quality Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$ (x=0.7 and 1.0) single crystals. In the normal states, we found a dramatic increase of the spin-lattice relaxation ($1/^{75}T_1$) from the x=0.7 to the x=1.0 samples. In KFe$_2$As$_2$, the ratio of $1/^{75}T_1TK_n^2$, where $^{75}K_n$ is the Knight shift, increases as temperature drops. These results indicate the existence of a new type of spin fluctuations in KFe$_2$As$_2$ which is accustomed to...

Source: http://arxiv.org/abs/0908.4369v2

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Sep 22, 2013
09/13

by
Michael Herrmann; Jens D. M. Rademacher

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We consider infinite FPU-type atomic chains with general convex potentials and study the existence of monotone fronts that are heteroclinic travelling waves connecting constant asymptotic states. Iooss showed that small amplitude fronts bifurcate from convex-concave turning points of the force. In this paper we prove that fronts exist for any asymptotic states that satisfy certain constraints. For potentials whose derivative has exactly one turning point these constraints precisely mean that...

Source: http://arxiv.org/abs/0812.1712v2

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Sep 21, 2013
09/13

by
Maria Beltran; Dan Hooper; Edward W. Kolb; Zosia C. Krusberg

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Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated...

Source: http://arxiv.org/abs/0808.3384v2

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Sep 22, 2013
09/13

by
Ertan Göklü; Claus Lämmerzahl

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Space--time can be understood as some kind of space--time foam of fluctuating bubbles or loops which are expected to be an outcome of a theory of quantum gravity. One recently discussed model for this kind of space--time fluctuations is the holographic principle which allows to deduce the structure of these fluctuations. We review and discuss two scenarios which rely on the holographic principle leading to holographic noise. One scenario leads to fluctuations of the space--time metric affecting...

Source: http://arxiv.org/abs/0908.3797v3

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Sep 22, 2013
09/13

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C. E. Creffield; F. Sols

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We study the response of a Bose-Einstein condensate to an unbiased periodic driving potential. By controlling the space and time symmetries of the driving we show how a directed current can be induced, producing a coherent quantum ratchet. Weak driving induces a regular behavior that is strongly governed by the interparticle interaction. Breaking both space and time symmetries is required to produce current flow. For strong driving the behavior becomes chaotic. The resulting effective...

Source: http://arxiv.org/abs/0908.0692v2

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Sep 23, 2013
09/13

by
Stefano Cardanobile; Stefan Rotter

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We introduce a nonlinear modification of the classical Hawkes process, which allows inhibitory couplings between units without restrictions. The resulting system of interacting point processes provides a useful mathematical model for recurrent networks of spiking neurons with exponential transfer functions. The expected rates of all neurons in the network are approximated by a first-order differential system. We study the stability of the solutions of this equation, and use the new formalism to...

Source: http://arxiv.org/abs/0904.1505v3

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Sep 22, 2013
09/13

by
Kenzo Ishikawa; Yutaka Tobita

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Coherence lengths of one particle states described by quantum wave functions are studied. We show that one particle states in various situations are not described by simple plane waves but are described by wave packets that are superpositions of plane waves. Wave packet is an approximate eigenstate of the free Hamiltonian and has a finite spatial size which we call the coherence length. The coherence lengths in the coordinate space and in the momentum space are studied in the present paper. We...

Source: http://arxiv.org/abs/0906.3938v3

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Sep 19, 2013
09/13

by
M. A. Prieto; J. Reunanen; K. R. W. Tristram; N. Neumayer; J. A. Fernandez-Ontiveros; M. Orienti; K. Meisenheimer

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Spectral energy distributions (SEDs) of the central few tens of parsec region of some of the nearest, most well studied, active galactic nuclei (AGN) are presented. These genuine AGN-core SEDs, mostly from Seyfert galaxies, are characterised by two main features: an IR bump with the maximum in the 2-10 micron range, and an increasing X-ray spectrum in the 1 to ~200 keV region. These dominant features are common to Seyfert type 1 and 2 objects alike. Type 2 AGN exhibit a sharp drop shortward of...

Source: http://arxiv.org/abs/0910.3771v3

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Sep 21, 2013
09/13

by
Kwang-Chang Lai; Guey-Lin Lin; T. C. Liu

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We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters $\theta_{ij}$ as those given by the current global fit, we demonstrate by a statistical method that the accuracies in the measurements of energy-independent ratios $R\equiv\phi (\nu_{\mu})/(\phi (\nu_{e})+\phi (\nu_{\tau}))$ and $S\equiv\phi (\nu_e)/\phi (\nu_{\tau})$ among integrated neutrino flux should both be...

Source: http://arxiv.org/abs/0905.4003v3